This invention relates to display apparatus and particularly to controls for altering displayed data at a selectable rate.
Digital displays of symbols representing operating parameters are commonly used in electronic devices such as communications, navigation, and data processing equipment as well as in diverse test equipment, manufacturing equipment and control apparatus. Known devices employing manual controls for entering data altering the operating parameters and the display thereof have taken various forms utilizing encoders for detecting the position of a smoothly rotating shaft, such as shown in U.S. Pat. Nos. 3,665,323; 3,835,384; and 4,125,295. A less complex arrangement utilizing a single switch providing discrete inputs for unit data entry, or alternately, fast data entry at a fixed rate, is shown in U.S. Pat. No. 4,036,431.
A method utilizing a discrete input event for unit data entry plus fast data entry at a rate depending on the speed of successive discrete input events was desired. One solution to the problem involved counting the number of discrete events (such as the number of contacts of a multiple position rotary switch) occurring in a fixed interval, and incrementing the display by an input quantity in accordance with a preselected gain signal, e.g., a single contact detected during the interval resulted in changing the input quantity by one least-significant digit (LSD) of the display, and movement of the switch N positions per interval resulted in a change of M (LSD), where M was a preselected number greater than 1. The performance of the control was adequate but less than ideal because of limited resolution of the gain schedule and lack of proper "feel" of the control during fast operation.
Accordingly, it is an object of the present invention to provide an improved method and apparatus for entering data altering a digital display.
Another object of the invention is to provide an improved method and apparatus for rapidly varying a displayed digital data field of wide dynamic range with a single manual control.
The present invention, in accordance with one embodiment thereof, provides a digital display and a manual control having a plurality of tactile detents, the control being coupled to the display through a control unit, the latter serving to sense movement of the manual control from one detent to the next and update the display in accordance with the direction and the speed of movement of the control between successive detents. The control unit includes a counter which is preset to a predetermined value and then decremented at a fixed rate until a detent is detected or until the counter reaches a value representative of one least-significant unit of the display. Upon sensing movement of the control between detents, the control unit serves to add or subtract (depending on the direction of movement of the manual control clockwise or counterclockwise) the then current contents of the counter to the digital display field. The counter is then preset again to the predetermined value and again decremented at the fixed rate, thereby conditioning the control unit for sensing the next movement of the manual control between detents.